OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..68
MATHEMATICA
Select[ FromDigits /@ Flatten[ Table[ PadLeft[{7}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 18}], 1], PrimeQ[ # ] &]
Select[Union[Flatten[Table[FromDigits[PadLeft[{7}, n, d]], {n, 15}, {d, 9}]]], PrimeQ] (* Harvey P. Dale, Nov 15 2020 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Robert G. Wilson v, Nov 22 2003
STATUS
approved